This proposal seeks partial support for the Fourth International Workshop on Chromosomes in Solid Tumors (IWCST) to be held February 24-26, 1991 at the Doubletree Hotel in Tucson, Arizona. The specific aims of this Workshop include: first, stimulating interest in and surveying the current state of knowledge of human solid tumor karyology. Second, bringing together recognized experts in the areas of cancer cytogenetics and molecular genetics in an integrated, organized and timely attempt to focus and disseminate the most recent advances in the areas of tumor karyology. Third, to begin to focus attention on possible clinical correlations of chromosome change in human solid tumors, including diagnostic and prognostic utility of chromosome change in solid tumors.